After you have opened a VHF power amplifier to make internal tuning adjustments, what should you do before you turn the amplifier on?

VHF power amplifiers operate using potentially lethal high voltages and generate intense radio frequency (RF) fields. The shielding in an amplifier acts as a critical safety barrier to protect the operator from accidental contact with these dangerous voltages and from hazardous RF exposure. Furthermore, the metallic shielding forms an essential part of the circuit's RF containment. Operating a VHF amplifier with the shields removed can disrupt the engineered grounding paths, leading to severe RF instability, dangerous parasitic oscillations, and unwanted interference. Bypassing power interlocks or testing without shielding compromises basic safety protocols. Interlocks are specifically designed to cut power when the cabinet is open to prevent life-threatening shock hazards, and bypassing them is highly dangerous.